1. Field of the Invention
This invention relates to object holders commonly utilized with cryostat microtomes.
2. Description of the Related Art
For histological analysis of tissue samples and determination of their physiological and pathological characteristics, microtomes are utilized to produce extremely thin sections for microscopic examination. A cryostat is a refrigerated box which includes a microtome. In some instances, it is desirable to fix the biological specimen cryogenically by cooling it to low temperatures on the order of about -10.degree. C. to about -50.degree. C. to produce a frozen "vitrified" sample for sectioning and analysis. Accordingly, cryostat microtomes have come into usage in which the microtome unit is mounted in a cooling enclosure. In such apparatus, the microtome is coupled to externally mounted controls to actuate and control the microtome. An illustrative cryostat microtome of such type is disclosed in U.S. Pat. No. 4,548,051 issued Oct. 22, 1985 to G. Moessner.
In recent years cryostat microtomes have become increasingly sophisticated, utilizing digital controls and monitoring devices affording a highly accurate, low-distortion sectioning operation. As an example, the Minotome.RTM. Digital Microtome-Cryostat, a cryostat microtome unit commercially available from International Equipment Company (Needham Heights, Mass.), is said to permit cutting of tissue sections with a thickness of from 2 to 42 microns, in precise 2 micron increments.
For such sectioning, the microtome typically employs an object holder comprising a specimen plate as a substrate element to which the tissue sample is affixed by an adhesive embedding medium. The specimen plate bearing such tissue sample then is clamped or otherwise fixedly positioned in the microtome apparatus, in proximity to a knife or blade which is translatable into cutting contact with the mounted specimen, to yield thin cut sections of tissue or other specimens for analysis.
With such precision sectioning ability, it is critically important in the operation of the microtome that the mounted specimen be retained in a spatially fixed position, since any movement of the specimen relative to the precision controlled cutting blade will produce sections of uneven thickness. Such variability in turn introduces a distortion and possible error into the subsequent microscopic analysis of the tissue, and may lead to mis-characterization or mis-diagnosis of the tissue, or else require discarding of the sample and repetition of the sectioning effort.
The requirement that the specimen plate be fixedly positioned and positionally constant during the sectioning operation, and the capability of the specimen holder to be relatively repositioned for subsequent sectioning operations, are frequently at odds with one another in the specimen plate assemblies which have been devised to date. There have been a number of object holders and microtome assemblies that have been devised to address this problem. As one can see from the different configurations of object holders shown as examples in FIGS. 2-10, it is clear that a wide variety of structures may be used to accomplish the same purpose.
Examples of object holders include the Minot.RTM. object holder of the International Equipment Company (Needham Heights, Mass.), used in the International Minot Custom Microtome. The object holder features a specimen plate and stem and is fastened to the microtome generally by a screw pressure on the side of the stem which is inserted into a clamp device featuring an opening communicating with a generally spherical interior cavity. Other object holders are discussed in the description of the invention herein.
The co-pending parent U.S. patent application Ser. No. 07/409,459, provides a specimen holder mounting structure which accommodates selective fixed positioning of a ball-mounted specimen plate in a manner which is highly resistant to movement during operation of the microtome, and which at the same time is readily selectively repositionable to different orientations. The specimen holder mounting structure utilizes only a single adjustment element. The ball-mounted specimen plate is readily adjustable, both rotationally and translationally, to a subsequently desired fixed position. The disclosure of this copending application is incorporated herein by reference.
The above microtome specimen (object) holders are traditionally fabricated out of various metals such as brass or stainless steel. Due to the smoothness of fabrication of these metallic holders and their hardness, any of the previous holders even if held by contact with two or more points of the microtome's holding mechanism may be susceptible to slippage or rotation during the cutting operation or due to vibrations or movements of the microtome.
It is therefore an object of this invention to provide a microtome object holder which is compressible, and temporarily deformable so that it can be held more firmly in the microtome.
Because of the material and sometimes the cost of construction, prior object holders are also often considered permanent and are not disposable. The non-disposable nature of the holders may require that the user take the time to sterilize the holder if specimens present risks to the user or could possibly contaminate subsequent specimens on the holder or the technician. Thus, if the specimen possibly contains a hazardous agent, such as HIV or hepatitis virus, the person using the microtome may wish to dispose of the contaminated object holder and use a new uncontaminated object holder.
It is therefore a further object of this invention to provide a microtome object holder which is disposable.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.